Non-aqueous electrolyte for lithium ion battery and lithium ion battery

ABSTRACT

The application provides a non-aqueous electrolyte for lithium ion battery. The non-aqueous electrolyte for lithium ion battery comprises a compound A represented by formula I and a compound B represented by formula II, 
     
       
         
         
             
             
         
       
     
     In formula I, R 1 , R 2  and R 3  are independently selected from C1-C5 alkyl or haloalkyl, C2-C5 unsaturated hydrocarbon group or unsaturated halohydrocarbon group, and at least one of R 1 , R 2  and R 3  is the unsaturated hydrocarbon group or unsaturated halohydrocarbon group; In formula II, R 4 , R 5 , R 6 , R 7 , R 8  and R 9  are each independently selected from one of hydrogen atom, fluorine atom and C1-C5 group. The non-aqueous electrolyte for lithium ion battery provided by the application enables the battery to have excellent cycle performance and high-temperature storage performance through the synergistic effect of the compound A and the compound B.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of U.S. patentapplication Ser. No. 16/490,899 filed on Sep. 4, 2019, which is anational phase application of PCT application No. PCT/CN2017/089734filed on Jun. 23, 2017, which in turn claims the benefit of ChinesePatent Application No. 201710297453.9 filed on Apr. 28, 2017. Thecontents of the above-identified applications are hereby incorporated byreference in their entirety.

TECHNICAL FIELD

The invention relates to the field of lithium ion batteries, moreparticularly, to a non-aqueous electrolyte for lithium ion battery andlithium ion battery.

BACKGROUND

Consumer digital and electronic products require higher and higherenergy density of batteries, which makes the current commercial lithiumion batteries difficult to meet the requirements. At present, theeffective way to improve the battery energy density is to increase theworking voltage of the lithium ion battery. The improvement of theworking voltage of lithium ion battery can improve the battery energydensity, however at the same time, the improvement of the workingvoltage can deteriorate the performance of battery. Because, on the onehand, the crystal structure of the positive electrode of battery isunstable under high voltage. In the process of charging and discharging,the crystal structure of the positive electrode of battery willcollapse, resulting in deterioration of performance. On the other hand,under high voltage, the surface of the positive electrode is in a highoxidation state with high activity, which is easy to catalyze theoxidative decomposition of electrolyte, and the decomposition productsof the electrolyte could easily deposit on the surface of the positiveelectrode, blocking the diffusion channel of lithium ions, thusdeteriorating the performance of the battery.

In its Chinese patent application, Japan's Matsushita ElectricIndustrial Co., Ltd. has disclosed an electrolyte containing a compoundof (R_(1a))P═(O)(OR_(2a))(OR_(3a)) (wherein R_(1a), R_(2a) and R_(3a)each independently represent an aliphatic hydrocarbon group having 7 to12 carbon atoms), which effectively controls the decrease in dischargecapacity and the decrease in battery performances duringhigh-temperature storage that occur as charging and discharging cyclesproceed. However, a large number of studies have found that althoughunsaturated phosphate ester can improve the high-temperature storage andhigh-temperature cycle performances of batteries, the high-temperaturestorage and cycle performances still cannot meet the needs of themarket.

SUMMARY

The invention aims to provide a non-aqueous electrolyte for lithium ionbattery with better high-temperature cycle performance, and aims tosolve the problem that the high-temperature storage and cycleperformances of the existing non-aqueous electrolyte for lithium ionbattery containing unsaturated phosphate ester cannot meet marketdemand.

The non-aqueous electrolyte for lithium ion battery provided by thepresent application, comprises a compound A represented by formula I anda compound B represented by formula II,

In formula I, R₁, R₂ and R₃ are independently selected from C1-C5 alkylor haloalkyl, C2-C5 unsaturated hydrocarbon group or unsaturatedhalohydrocarbon group, and at least one of R₁, R₂ and R₃ is theunsaturated hydrocarbon group or unsaturated halohydrocarbon group;

In formula II, R₄, R₅, R₆, R₇, R₈ and R₉ are each independently selectedfrom one of hydrogen atom, halogen atom and C1-C5 group.

Preferably, the C1-C5 group is selected from a hydrocarbon group,halogenated hydrocarbon group, oxygen-containing hydrocarbon group,silicon-containing hydrocarbon group, and cyano-substituted hydrocarbongroup.

Preferably, R₄, R₅, R₆, R₇, R₈ and R₉ are each independently selectedfrom a hydrogen atom, fluorine atom, methyl group, ethyl group, methoxylgroup, ethyoxyl group, triethylsiloxy group, cyano group ortrifluoromethyl group.

Preferably, the compound B comprises one or more of compounds 1-9represented by the following structural formulae,

Preferably, the percentage mass content of the compound B is 0.1-5%based on the total mass of the non-aqueous electrolyte for lithium ionbattery being 100%.

Preferably, in the compound A, C1-C5 alkyl is selected from one ofmethyl, ethyl, propyl, isopropyl and butyl; The C1-C5 haloalkyl isselected from one of monofluoromethyl, difluoromethyl, trifluoromethyl,2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl,3,3-difluoropropyl, 3,3,3-trifluoropropyl and hexafluoroisopropyl; TheC2-C5 unsaturated hydrocarbon group is selected from one of vinyl,allyl, 3-butenyl, isobutylenyl, 4-pentenyl, ethynyl, propargyl,3-butynyl, and 1-methyl-2-propynyl.

Preferably, the compound A is at least one selected from the groupconsisting of tripropargyl phosphate, dipropargyl methyl phosphate,dipropargyl ethyl phosphate, dipropargyl propyl phosphate,trifluoromethyl dipropargyl phosphate, dipropargyl 2,2,2-trifluoroethylphosphate, dipropargyl 3,3,3-trifluoropropyl phosphate,hexafluoroisopropyl dipropargyl phosphate, triallyl phosphate, diallylmethyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate,trifluoromethyl diallyl phosphate, 2,2,2-trifluoroethyl diallylphosphate, diallyl 3,3,3-trifluoropropyl phosphate or diallylhexafluoroisopropyl phosphate.

Preferably, the percentage mass content of the compound A is less than2% based on the total mass of the non-aqueous electrolyte for lithiumion battery being 100%.

And, a lithium ion battery, comprises a positive electrode, a negativeelectrode, a separator interposed between the positive electrode and thenegative electrode, and an electrolyte, wherein the electrolyte is thenon-aqueous electrolyte for lithium ion battery.

Preferably, the positive electrode comprises a positive electrode activematerial, and the positive electrode active material is at least one ofLiNi_(x)Co_(y)Mn_(z)L_((1-x-y-z))O₂, LiCo_(x′)L_((1-x′))O₂,LiNi_(x″)L′_(y′)Mn_((2-x″-y′))O₄ and Li_(z′)MPO₄, wherein, L is at leastone of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1,0<x+y+z≤1, 0<x′≤1, 0.3≤x″≤0.6, 0.01≤y′≤0.2, L′ is at least one of Co,Al, Sr, Mg, Ti, Ca, Zr, Zn, Si and Fe; 0.5≤z′≤1, M is at least one ofFe, Mn and Co.

The non-aqueous electrolyte for lithium ion battery provided by theapplication contains both the compound A and compound B, which caneffectively improve the high-temperature storage performance and cycleperformance of the battery, so that the lithium ion battery containingthe non-aqueous electrolyte has better cycle performance andhigh-temperature storage performance.

The lithium ion battery provided by the application contains theabove-mentioned non-aqueous electrolyte, which enables the lithium ionbattery to have both better cycle performance and high-temperaturestorage performance.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

In order to make the technical problems to be solved, technicalsolutions and beneficial effects more apparent and clearer, the presentapplication will be described in further detail below with reference toembodiments. It should be understood that the specific embodimentsdescribed herein are only for the purpose of explaining the presentinvention and are not intended to limit the present invention.

The non-aqueous electrolyte for lithium ion battery provided by thepresent application, comprises a compound A represented by formula I anda compound B represented by formula II,

In formula I, R₁, R₂ and R₃ are independently selected from C1-C5 alkylor haloalkyl, C2-C5 unsaturated hydrocarbon group or unsaturatedhalohydrocarbon group, and at least one of R₁, R₂ and R₃ is theunsaturated hydrocarbon group or unsaturated halohydrocarbon group;

In formula II, R₄, R₅, R₆, R₇, R₈ and R₉ are each independently selectedfrom one of hydrogen atom, halogen atom and C1-C5 group.

In the embodiments of the invention, C2-C5 indicates that the number ofcarbon atoms is 2-5, similarly, C1-C5 indicates that the number ofcarbon atoms is 1-5.

Preferably, in the compound A, C1-C5 alkyl is selected from one ofmethyl, ethyl, propyl, isopropyl and butyl; The C1-C5 haloalkyl isselected from one of monofluoromethyl, difluoromethyl, trifluoromethyl,2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl,3,3-difluoropropyl, 3,3,3-trifluoropropyl and hexafluoroisopropyl; TheC2-C5 unsaturated hydrocarbon group is selected from one of vinyl,allyl, 3-butenyl, isobutylenyl, 4-pentenyl, ethynyl, propargyl,3-butynyl, and 1-methyl-2-propynyl.

Preferably, the compound A is at least one selected from the groupconsisting of tripropargyl phosphate, dipropargyl methyl phosphate,dipropargyl ethyl phosphate, dipropargyl propyl phosphate,trifluoromethyl dipropargyl phosphate, dipropargyl 2,2,2-trifluoroethylphosphate, dipropargyl 3,3,3-trifluoropropyl phosphate,hexafluoroisopropyl dipropargyl phosphate, triallyl phosphate, diallylmethyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate,trifluoromethyl diallyl phosphate, 2,2,2-trifluoroethyl diallylphosphate, diallyl 3,3,3-trifluoropropyl phosphate or diallylhexafluoroisopropyl phosphate. The preferred compound A is morefavorable for improving the high-temperature storage performance andcycle performance of the battery, and is better for improving thebattery performance when used in combination with the compound B.

Preferably, the percentage mass content of the compound A is less than2% based on the total mass of the non-aqueous electrolyte for lithiumion battery being 100%.

The non-aqueous electrolyte for lithium ion battery provided by theembodiments of the invention contains a compound A represented bystructural formula I, and the compound A can form a film on the surfaceof the positive electrode of the battery during the formation process,thereby hindering the continuous decomposition of the electrolyte on theelectrode surface, hence improving the high-temperature storageperformance and cycle performance of the battery. However, theelectrolyte obtained by using the compound A as an additive still haslimited high-temperature storage performance and cycle performance andcannot meet the use requirements.

In the embodiments of the invention, on the basis of the compound Arepresented by structural formula I above, the compound B represented bystructural formula II was added to the non-aqueous electrolyte for thelithium ion battery. Through the combined use of the compound A and thecompound B, films are effectively formed on the positive electrode andthe negative electrode, and the high-temperature cycle performance andthe high-temperature storage performance of the battery can be furtherimproved.

Preferably, the C1-C5 group is selected from a hydrocarbon group,halogenated hydrocarbon group, oxygen-containing hydrocarbon group,silicon-containing hydrocarbon group, and cyano-substituted hydrocarbongroup.

Further preferably, R₄, R₅, R₆, R₇, R₈ and R₉ are each independentlyselected from a hydrogen atom, fluorine atom, methyl group, ethyl group,methoxyl group, ethyoxyl group, triethylsiloxy group, cyano group ortrifluoromethyl group.

Specifically preferably, the compound B comprises one or more ofcompounds 1-9 represented by the following structural formulae,

The above-mentioned preferred compound B can work better with thecompound A, so as to give the lithium ion battery with excellentintegral performance (including cycle performance and high-temperaturestorage performance).

It is further preferred that the percentage mass content of the compoundB is 0.1-5% based on the total mass of the non-aqueous electrolyte forlithium ion battery being 100%. When the percentage mass content of thecompound B is less than 0.1%, it is not favorable to the film formationof the compound B on the negative electrode, and the improvement effecton cycle performance is reduced; When the percentage mass content of thecompound B is more than 5%, the compound B cannot be fully and uniformlydissolved in the non-aqueous electrolyte, and the film formation on theelectrode interface is relatively thick, thus increasing the batteryimpedance to a certain extent and deteriorating the low-temperatureperformance of the battery.

The synthesis method of the compound B represented by formula I isconventional, for example, the compound B can be prepared by esterexchange reaction between polyol (such as erythritol, xylitol, etc.) andcarbonate (such as dimethyl carbonate, diethyl carbonate, vinylcarbonate, etc.) in the presence of basic catalyst. An example of thesynthetic route is as follows:

The fluorine-containing compound in compound B is prepared by:fluorinating the corresponding carbonate and mixture F₂/N₂, and thenrecrystallizing or purifying by column chromatography. An example of thesynthetic route is as follows:

The cyano group-containing compound in compound B is prepared by: thechlorination reaction of the corresponding carbonate and sulfonylchloride, then reacting with NaCN or KCN, and then recrystallizing orpurifying by column chromatography. An example of the synthetic route isas follows:

The trimethylsilanolate-containing compound in the compound B isprepared by: the substitution reaction of the corresponding hydroxycarbonate and silazane, then recrystallizing or purifying by columnchromatography. An example of the synthetic route is as follows:

Further preferably, the percentage mass content of the compound B is0.1-2% based on the total mass of the non-aqueous electrolyte forlithium ion battery being 100%.

It is understood that if the non-aqueous electrolyte for lithium ionbattery contains one of the above substances, the content is the contentof the one substance; If the non-aqueous electrolyte for lithium ionbattery contains a plurality of the above substances, the content is thesum of the contents of the plurality of substances.

The non-aqueous electrolyte for lithium ion battery provided by theembodiment of the invention contains both the compound A and compound B,which can effectively improve the high-temperature storage performanceand high-temperature cycle performance of the battery, so that thelithium ion battery containing the non-aqueous electrolyte has bettercycle performance and high-temperature storage performance.

Based on the above embodiments, it is preferred that the lithium ionnon-aqueous electrolyte further comprises at least one of unsaturatedcyclic carbonate compounds, fluorine-substituted cyclic carbonatecompounds, and sultone compounds.

Preferably, the unsaturated cyclic carbonate compound includes at leastone of vinylene carbonate (VC) and vinyl ethylene carbonate (VEC). Thefluorine-substituted cyclic carbonate compound includes fluoroethylenecarbonate (FEC). The sultone compound is selected from at least one of1,3-propane sultone (1,3-PS), 1,4-butane sultone (1,4-BS), and1,3-propene sultone (PST). The content of unsaturated cyclic carbonatecompound is 0.1-5% based on the total mass of the non-aqueouselectrolyte for lithium ion battery being 100%.

The content of fluorine-substituted cyclic carbonate compound is 0.1-30%based on the total mass of the non-aqueous electrolyte for lithium ionbattery being 100%.

The percentage mass content of sultone compound is 0.1-5% based on thetotal mass of the non-aqueous electrolyte for lithium ion battery being100%.

As is known to those skilled in the art, the main components in thenon-aqueous electrolyte for lithium ion battery are non-aqueous organicsolvents, lithium salts and additives. In the present application,compound A and compound B are additives. The content of non-aqueousorganic solvent and lithium salt is conventional, and it can be adjustedaccordingly after the content of the additive including compound A andcompound B is determined.

Preferably, the lithium salt is selected from one or more of LiPF₆,LiBF₄, LiBOB, LiDFOB, LiN(SO₂CF₃)₂, LiN(SO₂C₂F₅)₂, LiC(SO₂CF₃)₃ andLiN(SO₂F)₂. The lithium salt content in the non-aqueous electrolyte forlithium ion battery is 0.1-15%.

Preferably, the non-aqueous electrolyte for lithium ion batterycomprises a non-aqueous organic solvent, and the non-aqueous organicsolvent is at least one of vinyl carbonate, propylene carbonate,butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethylcarbonate and methyl propyl carbonate. More preferably, the non-aqueousorganic solvent is a composition of vinyl carbonate, diethyl carbonateand methyl ethyl carbonate.

And, the invention also provides a lithium ion battery, comprising apositive electrode, a negative electrode, a separator interposed betweenthe positive electrode and the negative electrode, and an electrolyte,wherein the electrolyte is the non-aqueous electrolyte for lithium ionbattery.

Preferably, the positive electrode comprises a positive electrode activematerial, and the positive electrode active material is at least one ofLiNi_(x)Co_(y)Mn_(z)L_((1-x-y-z))O₂, LiCo_(x′)L_((1-x′))O₂,LiNi_(x″)L′_(y′)Mn_((2-x″-y′))O₄, Li_(z) and MPO₄, wherein, L is atleast one of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1,0<x+y+z≤1, 0<x′≤1, 0.3≤x″≤0.6, 0.01≤y′≤0.2, L′ is at least one of Co,Al, Sr, Mg, Ti, Ca, Zr, Zn, Si and Fe; 0.5≤z′≤1, M is at least one ofFe, Mn and Co.

In the embodiment of the present invention, the negative electrode andthe separator are not specifically limited, they can be the conventionalones in the art.

The lithium ion battery provided by the application contains theabove-mentioned non-aqueous electrolyte, which enables the lithium ionbattery to have both better cycle performance and high-temperaturestorage performance.

The following description will be made with reference to specificembodiments.

Embodiment 1

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 1, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 2

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 2, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 3A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphitebattery, comprises a positive electrode, a negative electrode, aseparator interposed between the positive electrode and the negativeelectrode, and an electrolyte, wherein the electrolyte is a non-aqueouselectrolyte and comprises the following components in percentage by massas shown in Table 1 of embodiment 3, based on the total weight of thenon-aqueous electrolyte taken as 100% by weight.

Embodiment 4

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 4, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 5

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 5, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 6

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 6, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 7

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 7, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 8

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 8, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 9

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 9, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 10

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 10, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 11

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 11, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 12

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of embodiment 12, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Embodiment 13

A LiNi_(0.5)Co_(0.15)Al_(0.05)O₂/Si—C battery, comprises a positiveelectrode, a negative electrode, a separator interposed between thepositive electrode and the negative electrode, and an electrolyte,wherein the electrolyte is a non-aqueous electrolyte and comprises thefollowing components in percentage by mass as shown in Table 2 ofembodiment 13, based on the total weight of the non-aqueous electrolytetaken as 100% by weight.

Embodiment 14

A LiNi_(0.5)Co_(0.15)Al_(0.05)O₂/Si—C battery, comprises a positiveelectrode, a negative electrode, a separator interposed between thepositive electrode and the negative electrode, and an electrolyte,wherein the electrolyte is a non-aqueous electrolyte and comprises thefollowing components in percentage by mass as shown in Table 2 ofembodiment 14, based on the total weight of the non-aqueous electrolytetaken as 100% by weight.

Comparative Example 1

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of Comparative Example 1, based on the total weight of thenon-aqueous electrolyte taken as 100% by weight.

Comparative Example 2

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of Comparative Example 2, based on the total weight of thenon-aqueous electrolyte taken as 100% by weight.

Comparative Example 3

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of Comparative Example 3, based on the total weight of thenon-aqueous electrolyte taken as 100% by weight.

Comparative Example 4

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of Comparative Example 4, based on the total weight of thenon-aqueous electrolyte taken as 100% by weight.

Comparative Example 5

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of Comparative Example 5, based on the total weight of thenon-aqueous electrolyte taken as 100% by weight.

Comparative Example 6

A 4.4V LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂/artificial graphite battery,comprises a positive electrode, a negative electrode, a separatorinterposed between the positive electrode and the negative electrode,and an electrolyte, wherein the electrolyte is a non-aqueous electrolyteand comprises the following components in percentage by mass as shown inTable 1 of Comparative Example 6, based on the total weight of thenon-aqueous electrolyte taken as 100% by weight.

Comparative Example 7

A LiNi_(0.5)Co_(0.15)Al_(0.05)O₂/Si—C battery, comprises a positiveelectrode, a negative electrode, a separator interposed between thepositive electrode and the negative electrode, and an electrolyte,wherein the electrolyte is a non-aqueous electrolyte and comprises thefollowing components in percentage by mass as shown in Table 2 ofComparative Example 7, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

Comparative Example 8

A LiNi_(0.5)Co_(0.15)Al_(0.05)O₂/Si—C battery, comprises a positiveelectrode, a negative electrode, a separator interposed between thepositive electrode and the negative electrode, and an electrolyte,wherein the electrolyte is a non-aqueous electrolyte and comprises thefollowing components in percentage by mass as shown in Table 2 ofComparative Example 8, based on the total weight of the non-aqueouselectrolyte taken as 100% by weight.

The Embodiments 1-14 and the Comparative Examples 1-8 were tested forperformance, and the test parameters and test methods are as follows:

(1) High-temperature cycle performance is demonstrated by testing thecapacity retention rate after N cycles at 45° C. 1C. The specific methodis as follows: at 45° C., the formed battery was charged to 4.4V with 1Cconstant current/constant voltage, the cutoff current was 0.01C, andthen discharged to 3.0V with 1C constant current. After suchcharging/discharging for N cycles, the capacity retention rate after theNth cycle was calculated to evaluate its high-temperature cycleperformance.

The calculation formula of the Nth cycle capacity retention rate at 45°C. 1C is as follows:

The Nth cycle capacity retention rate (%)=(the Nth cycle dischargecapacity/the first cycle discharge capacity)*100%.

(2) Room-temperature cycle performance is demonstrated by testing thecapacity retention rate after N cycles at 25° C. 1C. The specific methodis as follows: at 25° C., the formed battery was charged to 4.4V with 1Cconstant current/constant voltage, the cutoff current was 0.01C, andthen discharged to 3.0V with 1C constant current. After suchcharging/discharging for N cycles, the capacity retention rate after theNth cycle was calculated to evaluate its room-temperature cycleperformance.

The calculation formula of the Nth cycle capacity retention rate at 25°C. 1C is as follows:

The Nth cycle capacity retention rate (%)=(the Nth cycle dischargecapacity/the first cycle discharge capacity)*100%.

(3) Test method for capacity retention rate, capacity recovery rate andthickness expansion rate after N days of storage at 60° C.: the formedbattery was charged to 4.4V at room temperature with 1C constantcurrent/constant voltage, the cutoff current was 0.01C, then dischargedto 3.0V with 1C constant current, the initial discharge capacity of thebattery was measured, then charged to 4.4V with 1C constantcurrent/constant voltage, the cutoff current was 0.01C, and the initialthickness of the battery was measured. Then the battery was stored at60° C. for N days, measured the thickness of the battery, discharged itto 3.0V with 1C constant current, measured the capacity retention of thebattery, then charged it to 4.4V with 1C constant current/constantvoltage, the cutoff current was 0.01C, then discharged it to 3.0V with1C constant current, then measured the recovery capacity. Thecalculation formulas for capacity retention rate and capacity recoveryrate are as follows:

Battery capacity retention rate (%)=(retention capacity/initialcapacity)*100%;

Battery capacity recovery rate (%)=(recovery capacity/initialcapacity)*100%;

Battery thickness expansion rate (%)=(thickness after N days −initialthickness)/initial thickness*100%.

The test results of Embodiments 1-18 and Comparative Examples 1-3 areshown in Table 1 below.

TABLE 1 The 500th The 300th cycle capacity cycle capacity After 30 daysof storage at 60° C. retention retention Capacity Capacity ThicknessOther rate (%) at rate (%) at retention recovery expansion Compound ACompound B additives 25° C. 1 C 45° C. 1 C rate (%) rate (%) rate (%)Embodiment Tripropargyl Compound 91.50 82.00 85.30 88.30 5.70 1phosphate: 1% 1: 1% Embodiment Tripropargyl Compound 91.40 81.10 85.5088.60 5.30 2 phosphate: 1% 3: 1% Embodiment Tripropargyl Compound 91.1081.90 85.40 87.90 4.90 3 phosphate: 1% 5: 1% Embodiment TripropargylCompound 90.50 79.50 82.00 84.10 6.10 4 phosphate: 1% 1: 0.1% EmbodimentTripropargyl Compound 91.20 80.00 83.00 85.60 5.50 5 phosphate: 1% 1:0.5% Embodiment Tripropargyl Compound 92.00 85.00 86.50 88.20 3.90 6phosphate: 1% 1: 2% Embodiment Tripropargyl Compound 91.00 81.00 83.5085.30 5.80 7 phosphate: 0.5% 1: 1% Embodiment Dipropargyl ethyl Compound90.00 80.10 81.50 83.30 6.30 8 phosphate: 1% 1: 1% EmbodimentHexafluoroisopropyl Compound 86.00 76.00 79.70 81.50 7.00 9 bis(propargyl) 1: 1% phosphate: 1% Embodiment Tripropargyl Compound VC: 1%92.70 84.50 85.80 88.80 5.60 10 phosphate: 1% 1: 1% EmbodimentTripropargyl Compound FEC: 1% 92.80 84.90 85.80 88.90 5.90 11 phosphate:1% 1: 1% Embodiment Tripropargyl Compound PS: 1% 92.90 85.10 85.20 89.305.60 12 phosphate: 1% 1: 1% Comparative Tripropargyl / 81.50 76.60 80.1083.20 8.20 Example 1 phosphate: 1% Comparative Dipropargyl ethyl / 70.0065.00 77.00 80.00 10.40 Example 2 phosphate: 1% ComparativeHexafluoroisopropyl / 66.00 60.00 75.00 77.00 12.50 Example 3 bis(propargyl) phosphate: 1% Comparative Tripropargyl VC: 1% 86.00 79.0081.00 84.00 10.00 Example 4 phosphate: 1% Comparative Tripropargyl FEC:1% 87.70 78.90 80.70 83.80 12.00 Example 5 phosphate: 1% ComparativeTripropargyl PS: 1% 87.10 79.10 81.20 84.30 11.90 Example 6 phosphate:1%

As is well known to those skilled in the art, the Embodiments andComparative Examples in Table 1 and Table 2 above include conventionalsolvents, lithium salts and other substances in addition to the listedsubstances, which are not specifically described in the presentapplication, and, in the electrolyte, the weight other than the listedabove is the content of solvent and lithium salt.

Referring to Table 1, Embodiments 1-12 and Comparative Examples 1-6 arecompared. Both compound A and compound B were added to the lithium ionnon-aqueous electrolyte of Embodiments 1-12, and only Compound A wasadded to the lithium ion non-aqueous electrolyte of Comparative Examples1-6. The results show that compared with Comparative Examples 1-6, thebatteries made with the lithium ion non-aqueous electrolyte containingboth Compound A and Compound B have obviously improved cycle performanceat 25° C. and 45° C., as well as better storage performance at 60° C. Itcan be seen that the combined use of compound A and compound B can havesynergistic effect, which can obviously improve the high-temperaturestorage and high-temperature cycle performances of the battery.

The test results of Embodiments 13-14 and Comparative Examples 7-8 areshown in Table 2 below.

TABLE 2 The 400th cycle The 200th cycle After 14 days of storage at 60°C. capacity retention capacity retention Capacity Capacity Thicknessrate (%) at room rate (%) at retention recovery expansion Compound ACompound B temperature 1 C 45° C. 1 C rate (%) rate (%) rate (%)Embodiment Tripropargyl Compound 80.3 80.6 80.5 82.6 9.1 13 phosphate:1% 1: 1% Embodiment Dipropargyl Compound 80.8 81.3 80.4 82.5 10 14 ethyl1: 1% phosphate: 1% Comparative Tripropargyl 70.2 72.1 70.3 72.8 18Example 7 phosphate: 1% Comparative Dipropargyl 69.4 60.8 69.5 72.1 20Example 8 ethyl phosphate: 1%

Referring to Table 2, Embodiments 13, 14 and Comparative Examples 7, 8are compared. Both compound A and compound B were added to the lithiumion non-aqueous electrolyte of Embodiments 13 and 14. The results showthat the lithium ion non-aqueous electrolyte containing only compound Ahas relatively low room-temperature cycle performance andhigh-temperature cycle performance, and obviously poor high-temperaturestorage performance. On the basis of adding compound A and B, the normaltemperature cycle performance and high temperature cycle performance ofthe battery are improved.

The above descriptions are only preferred embodiments and are notintended to limit the present invention. Any modifications, equivalentsubstitutions and improvements made within the spirit and principles ofthe present invention shall be included within the scope of protectionof the present invention.

What is claimed is:
 1. A non-aqueous electrolyte for a lithium ion battery, comprising a compound A represented by formula I and a compound B represented by formula II,

in formula I, R₁, R₂ and R₃ are independently selected from a C1-C5 alkyl group or a C1-C5 haloalkyl group, a C2-C5 unsaturated hydrocarbon group or a C2-C5 unsaturated halohydrocarbon group, and at least one of R₁, R₂ and R₃ is the unsaturated hydrocarbon group or unsaturated halohydrocarbon group; in formula II, R₄, R₅, R₆, R₇, R₈ and R₉ are each independently selected from one of a hydrogen atom, a fluorine atom and a C1-C5 group.
 2. The non-aqueous electrolyte for a lithium ion battery of claim 1, wherein in formula II, the C1-C5 group is selected from a hydrocarbon group, a halogenated hydrocarbon group, an oxygen-containing hydrocarbon group, a silicon-containing hydrocarbon group, and a cyano-substituted hydrocarbon group.
 3. The non-aqueous electrolyte for a lithium ion battery of claim 1, wherein in formula I, R₄, R₅, R₆, R₇, R₈ and R₉ are each independently selected from a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a methoxyl group, an ethyoxyl group, a triethylsiloxy group, a cyano group or a trifluoromethyl group.
 4. The non-aqueous electrolyte for a lithium ion battery of claim 1, wherein the compound B comprises one or more of compounds 1-9 represented by the following structural formulae,


5. The non-aqueous electrolyte for a lithium ion battery of claim 1, wherein the percentage mass content of the compound B is 0.1-5% based on the total mass of the non-aqueous electrolyte for lithium ion battery being 100%.
 6. The non-aqueous electrolyte for a lithium ion battery of claim 1, wherein in the compound A, the C1-C5 alkyl group is selected from one of methyl, ethyl, propyl, isopropyl and butyl; the C1-C5 haloalkyl group is selected from one of monofluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3,3-difluoropropyl, 3,3,3-trifluoropropyl and hexafluoroisopropyl; the C2-C5 unsaturated hydrocarbon group is selected from one of vinyl, allyl, 3-butenyl, isobutylenyl, 4-pentenyl, ethynyl, propargyl, 3-butynyl, and 1-methyl-2-propynyl.
 7. The non-aqueous electrolyte for a lithium ion battery of claim 6, wherein the compound A comprises at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, trifluoromethyl dipropargyl phosphate, dipropargyl 2,2,2-trifluoroethyl phosphate, dipropargyl 3,3,3-trifluoropropyl phosphate, hexafluoroisopropyl dipropargyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, trifluoromethyl diallyl phosphate, 2,2,2-trifluoroethyl diallyl phosphate, diallyl 3,3,3-trifluoropropyl phosphate or diallyl hexafluoroisopropyl phosphate.
 8. The non-aqueous electrolyte for a lithium ion battery of claim 1, wherein the percentage mass content of the compound A is greater than 0%, and less than 2% based on the total mass of the non-aqueous electrolyte for lithium ion battery being 100%.
 9. A lithium ion battery, comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the electrolyte is the non-aqueous electrolyte for a lithium ion battery of claim
 1. 10. The lithium ion battery of claim 9, wherein the positive electrode comprises a positive electrode active material, and the positive electrode active material is at least one of LiNi_(x)Co_(y)Mn_(z)L_((1-x-y-z))O₂, LiCo_(x′)L_((1-x))O₂, LiNi_(x″)L′_(y′)Mn_((2-x″-y′))O₄ and Li_(z′)MPO₄, wherein, L is at least one of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0<x+y+z≤1, 0<x′≤1, 0.3≤x″≤0.6, 0.01≤y′≤0.2, L′ is at least one of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si and Fe; 0.5≤z′≤1, M is at least one of Fe, Mn and Co. 